1. Field of the Invention
The present invention relates to a propylene-1-butene copolymer, and a thermoplastic resin composition. More particularly, it relates to a novel propylene-1-butene copolymer which gives a thermoplastic resin composition having excellent flexibility, tensile elongation characteristics, scratch resistance and transparency when mixing with a resin such as polypropylene, and a thermoplastic resin composition containing said propylene-1-butene copolymer and a polyolefin resin.
2. Description of the Related Art
The propylene-1-butene copolymer is used in melt molded articles (e.g. film, sheet, etc.) as a soft or semirigid resin material which is superior in transparency, surface non-tackiness, tensile characteristics, etc. It is blended with a resin such as polypropylene, etc., and is also used for improvement of heat sealability, impact resistance, etc., widely.
U.S. Pat. No. 2,918,457 discloses a propylene-1-butene copolymer produced by using titanium trichloride. Since the propylene-1-butene copolymer has high hardness, when using the propylene-1-butene copolymer for modification of polypropylene, it is effective for improvement of heat sealbility, impact resistance, etc., but the flexibility, tensile elongation characteristics and scratch resistance are not improved. Since the propylene-1-butene copolymer contains a low-molecular weight component, there also arose a problem that tackiness is remained on the surface of a molded article.
Japanese Patent Kokai Publication Nos. 53-79984, 54-85293, 60-38414, 62-119212 an 62-119213 disclose a propylene-1-butene copolymer containing no low-molecular weight component, and use thereof. Since these propylene-1-butene copolymers have high hardness, when using them for modification of polypropylene, the surface tackiness of the molded article is inhibited and the heat sealability and impact resistance are improved, but the flexibility, tensile elongation characteristics and scratch resistance are not improved.
Japanese Patent Kokai Publication No. 50-38787 discloses that an amorphous propylene-1-butene copolymer can be obtained by using a titanium trichloride catalyst at 140 to 250.degree. C. When using such a copolymer for modification of polypropylene, the flexibility, tensile elongation characteristics, scratch resistance and transparency are improved, but the properties such as flexibility, tensile elongation characteristics, scratch resistance and transparency are improved only some extent. These properties could be well improved by using much amount of propylene-1-butene copolymer, but properties such as strength and heat resistance become worse. Because the said propylene-1-butene copolymer has the heterogeneity of composition distribution and molecular weight distribution and has the significant amount of crystalline property derived from said heterogeneity, flexibility, tensile elongation characteristics, scratch resistance and transparency are improved, but strength and heat resistance are not sufficiently improved.
As the polypropylene thermoplastic resin composition containing the propylene-1-butene copolymer, for example, a polypropylene thermoplastic resin composition containing a propylene-1-butene copolymer having the crystallizability is disclosed in Japanese Patent Kokai Publication No. 8-12719. Furthermore, a polypropylene thermoplastic resin composition containing a propylene-1-butene copolymer having the crystallinity of 10to 30% is disclosed in Japanese Patent Kokai Publication No. 7-42367. However, these propylene-1-butene copolymers have high hardness and the flexibility imparting effect was not recognized in the polypropylene thermoplastic composition containing these propylene-1-butene copolymer.